The use of electrical and hydraulic controllers as a means for selective control of valves in large irrigation systems is widespread. Such controllers have been employed in large real estate development projects, golf courses, municipal projects, isolated sites, and other applications as is well known in the art. Typically, such irrigation systems are generally known to include a source of water, a valving network or system with associated pipes, and a controller, the controller being designed to selectively open and close valves so that water can be communicated to various outlets for a known period of time. Such controllers may either be electronic and coupled to solenoid valves or fluid actuated and connected to corresponding formed valves. Such controllers will invariably include a manually settable timing or measuring mechanism to enable irrigation on a programmed or preplanned basis.
Inasmuch as irrigation systems invariably experience failures or conditions at the site of irrigation otherwise change. numerous attempts have been made to address the problem of modifying the normal irrigation pattern in the presence of such changed conditions. In many cases, however, actual irrigation will be at a location which is remote from the person who is concerned with monitoring or operating the site.
Several alternatives exist for altering the normal irrigation pattern as preset on the controller from varying locations, but these have proven to be beset by a number of problems. Manual adjustment of such controllers in response to changed conditions has proven to be very time consuming, labor intensive, and generally too slow. It is also possible to have direct lines of communication to such sites, such as with direct telephone line modems. HOwever, this approach is very expensive and requires a separate dedicated phone line to every location where a plurality of irrigation sites are involved. Moreover, even a telephone lessee in this situation must dial every individual location separately, which is time consuming and costly.
It is also possible to communicate with such controllers through a radio link; however, it has proven difficult to obtain necessary radio licenses because of the large number of regulations and procedures that must be complied with and because of the ever-increasing proliferation of radio users. Further, transmit antennas and receivers are large and expensive. Moreover, with a traditional radio system, a problem of having ample communication power arises. For example, a 14 foot antenna might be necessary in many applications, and for one individual to own a transmitter and receiver having adequate geographical coverage capabilities is very uneconomical and inefficient. In addition, a traditional radio controller irrigation system can only reach areas covered by the transmitter.
The prior art reveals a number of approaches for communicating with an irrigation site during changed irrigation conditions, but these approaches have either been unduly expensive, have met with limited success, or are impractical for dealing with a large plurality of remote locations. For example, U.S. Pat. No. 4,185,650 describes a method and apparatus for trouble-shooting an irrigation system. This patent discloses a receiver electrically connected to a controller at a position between the timing apparatus and a station advance mechanism. However, in this system, the radio receiver is responsive to two transmitted signals, and the transmitter is located at the site of trouble.
U.S. Pat. No. 4,146,049 describes a traveling sprinkler radio controlled mechanism warning device and is directed to a mechanism for preventing over-watering by unattended traveling sprinklers. In this system, a radio transmitter and receiver means are used to transmit and receive a shut-off signal for a pump supplying water to the traveling sprinkler in the event that the sprinkler stops. The transmitter in this system, however, is located at the sprinkler and the receiver is at the pump. The transmitter is actually carried in this system by a traveling sprinkler.
Another system in U.S. Pat. No. 4,396,149 discloses an irrigation control system wherein moisture sensors are included in masts sunk in the ground. The masts at the site transmit soil moisture and weather data to a central computer. U.S. Pat. No. 4,209.131 also describes a computer-controlled irrigation system, wherein a central station and a plurality of remote field stations are involved. A computer in that system, via a communication path such as a radio channel, sends coded command messages to selected remote stations for activating valves and pumps for delivering pre-established quantities of water to selected fields. However,. this system requires the use of special computers and special programming machines, and also transmitting means appear to be required at the actual irrigation site. In addition, expensive computing and communication means must be separately acquired and used in connection with this technique.
Another system, disclosed in U.S. Pat. No. 4,626,984, teaches a remote computer system for controlling a plurality of irrigation systems, each system having a local controller including an intelligent remote unit, each intelligent remote unit having a computer with a stored program for independently operating the local controller. However, in this system, the controller must possess means to monitor and control parameters in order to operate properly.
U.S. Pat. No. 3,726,477 discloses an automated irrigation control system which uses a central transmitter to transmit coded citizen band radio signals to a plurality of stations. However, the radio transmitting means has elaborate encoding features and appears to be limited to local control of the stations. Further. for this system, each receiver has its own frequency, a limited number of channels are available, transmission is noisy and insecure, and the geographical coverage is minimal.
In summary, the existing approaches for modifying the behavior of a controller at an irrigation site involved complicated communication and computational systems and also entail significant additional communications and computational costs to the users and operators of such systems. Most of these systems do not permit control by a remote operator or transmitter for added convenience.
What is needed, therefore, is a simple mechanism by which irrigation control at a site can be modified with a minimum of communications and computer equipment, minimum of capital investment costs, and maximum of convenience to the user. It is also desirable that an inexpensive, non-capital intensive technique be found whereby the operation of an irrigation controller can be modified by a user or transmitter at a remote location. It is also desirable that a system be proved whereby a plurality of controllers can be modified by essentially using a simple system and a common communications signal, unhampered by geographical limitations on the irrigation site, the transmitter, or the location of the user.